This invention relates to methods of subjecting welded structures to heat treatment, and, more particularly, to a method of subjecting pipes, cylindrical vessels and other structures of large size in nuclear power plants, chemical plants, etc., to heat treatment, which is suitable for improving the residual stress occurring on the inner surface of these structures by welding.
It has been proposed to rely on heat treatment to improve the residual stress occurring on the inner surface of a welded structure by welding in, for example, in U.S. Pat. No. 4,229,235 however, no consideration has, been given to welded structures of large size in which difficulty is encountered in subjecting the whole of each weld to heat treatment by using a single heating member.